Sean Penn, Charlize Theron Heating Up

The reputedly gruff actor has been showing his softer side lately when it comes to new girlfriend Charlize Theron and her 3-year-old son Jackson.

Sunday, the 53-year-old actor was all smiles during an outing with Theron, 38, and Jackson at the Underwood Family Farm in Moorpark, Calif. Penn could be seen with his arms wrapped around Theron, nuzzling her neck, and playing the doting dad to Jackson, whom Theron adopted as a single mom.

Two days earlier, the new couple also engaged in a serious public display of affection.

The two Oscar winners went public with their romance at Penn's Jan. 11 Help Haiti Home gala, where they could be seen getting cozy with their arms around each other. Later Penn called her a "keeper," after Piers Morgan congratulated him on Theron.

According to Morgan, Penn told him, "She's a keeper, that's for sure… well, I'll do my best to keep her anyway."